This invention relates to cement dispersion agents. More particularly, this invention relates to cement dispersion agents capable of providing high fluidity to high-strength cement compounds with extremely low water-to-cement ratio and reducing the drop in the fluidity with the passage of time after mixing.
It has been known to use condensation products of naphthalene sulfonic acid and formaldehyde, condensation products of melamine sulfonic acid and formaldehyde or water-soluble vinyl copolymers as a cement dispersion agent. If such a prior art cement dispersion agent is used to produce a high-strength cement compound and, in particular, if it is desired to produce an ultra high-strength cement compound with extremely low water-to-cement ratio of less than 20% in order to obtain hardened concrete and mortar with compressive strength greater than 1100 kgf/cm.sup.2, however, neither condensation products of naphthalene sulfonic acid and formaldehyde nor condensation products of melamine sulfonic acid and formaldehyde is capable of providing any fluidity to such a cement compound. If use is made of water-soluble vinyl copolymers (such as disclosed in U.S. Pat. No. 4,962,173 and Japanese Patent Application Tokkai 3-93660), it is not possible to provide sufficient fluidity to such cement compounds and the drop in whatever fluidity that has been provided with the passage of time after mixing (referred to as the slump loss) is large. It now goes without saying that workability becomes extremely poor if sufficient fluidity cannot be provided to a cement compound and the slump loss is large.